After router association to L3vpn, one of the VM ip is not removed from router interface to BGPVPN

When a VPN associated to router is deleted and a same VPN is associated back to same router , there is race condition , where interface is not found in VpnInterfaceOp and remove event is being ignored. Hence interface remains in router VPN.

It is also seen that , one of interface from same subnet is swapped and others are not. Its due to race condition that exist in NeutronVpnManager where create and update can race with each other. Currently create uses DJC , where as update doesn't .